1. Field of the Invention
The present invention relates to a decomposition method for suitable for decomposition of a halogenated compound, and particularly suitable for a polyhalogenated compount such as PCB, and a decomposition apparatus therefor.
2. Description of the Related Art
Polyhalogenated biphenyl, particularly PCB is excellent in heat resistance, chemical resistance and electric insulating properties, and therefore has been heretofore widely used as a heating medium for heat treatment, additives for paint, ink and the like, and insulating agents for condensers and transformers.
However, recently, PCB was considered to be an environmental contamination material. However, it is difficult to dispose PCB because of physical and chemical stabilities thereof. Various studies and researches have been made and disclosed to make PCB harmless.
For example, (1) Japanese Patent Laid-Open No. 82,570/1974 publication, Japanese Patent Publication No. 39,290/1981 publication and Japanese Patent Laid Open No. 241,586/1990 disclose a method in which PCB is mixed or not mixed with alkaline metal, hydrogen gas or the like and subjected to thermal decomposition at a high temperature of 1200.degree. C to 1500.degree. C.
(2) Japanese Patent Laid-Open No. 63,005/1975 publication and Japanese Patent Publication No. 59,779/1986 publication disclose a method in which ultraviolet rays are irradiated on a mixture of PCB and hydrogen, a basic material or the like for photo-decomposition.
(3) Japanese Patent Laid-Open No. 205,510/1989 publication discloses a method in which alkaline metal oxide and glycols are added to PCB and subjected to chemical decomposition under the N.sub.2 gas atmosphere.
However, the above-described thermal decomposition method has problems in that an extremely high temperature is required, a large amount of energy is required, and polydibenzfuran chloride (PCDF) and dioxine which are much higher in toxicity than PCB are possibly generated due to the lowering of a burning temperature. Further, the photo-decomposition method using ultraviolet rays has a problem in that when only the ultraviolet rays or ultraviolet rays and ozone are merely used, the decomposition rate is low and the efficiency is poor. Moreover, the chemical decomposition method uses various chemicals, and has a problem in that the cost increases, and handling of chemicals is difficult, deteriorating workability.